1. Field of the Invention
The present invention relates to a disc-shaped optical information recording medium in which printing and drawing can be performed on the label surface (opposite to a light incidence plane) side thereof. Specifically, the present invention relates to an optical information recording medium of a type in which a printing and drawing region is extended to the inner peripheral side inside an information recording region for recording information by laser beam irradiation.
2. Description of the Related Technology
Disc-shaped optical information recording media such as CD-R, DVD±R, HD-DVD-R, and BD (blue-ray disc) have a structure in which a recording layer and a reflecting layer are formed on one of the surfaces of a light-transmitting substrate so that data can be recorded on the recording layer by laser beam irradiation of the other surface of the light-transmitting substrate. Also, in each of these optical information recording media, the surface opposite to the surface to be irradiated with a laser beam is generally used as a label surface on which a character, a symbol, a figure, a pattern, or a combination thereof is displayed as visible information by printing or the like.
Various types of optical information recording media have been proposed in which the display is performed with an ink jet printer or the like. For example, Japanese Unexamined Patent Application Publication No. 2004-139697 proposes an optical information recording medium including a disc-shaped light-transmitting substrate in which dummy grooves and a reflecting layer are provided in a portion corresponding to a clamping area, and an image forming layer is provided in a portion corresponding to a reflecting layer or another area of the substrate. The clamping area is provided around a central hole having a radius of 7.5 mm within a range from the center of the light-transmitting substrate to a radius of less than 22 mm. An information recording area is provided outside the clamping area, pre-grooves for tracking guide being formed in the information recording area.
However, in order to extend the image forming region of the above-described optical information recording medium, for example, as shown in FIG. 5, a reflecting layer 4 is provided on a recording layer 3 so that the inner peripheral side thereof extends to dummy grooves 2b beyond the inner peripheral edge 3a of the recording layer 3. In this case, grooves 4b formed in the surface of the reflecting layer 4 which is provided, without through the recording layer, on the region in which the dummy grooves 2b are formed is deeper than the grooves 4a formed in the surface of the reflecting layer 4 which is provided, through the recording layer 3, on the region in which pre-grooves 2a are formed. Therefore, the intensity of reflection of visible light from the surface (per unit area) of the reflecting layer 4 provided on the dummy grooves 2b is lower than that from the surface of the reflecting layer 4 provided on the pre-grooves 2a. Therefore, there occurs the problem of producing an annular portion with decreased brightness near the inner peripheral edge (a portion adjacent to a mirror portion 4d) of an ink-receiving layer as seen from the label surface side.